German Published Patent Application No. 197 14 784 describes a compact drive, which includes an electric motor, at whose one end face a gear unit is arranged, and at whose other end face a frequency converter is arranged. The electronics region and the motor region must be sealed with respect to the gear unit. In this context, it is disadvantageous that the axial length is large and that a power take-off can only be provided at one end face of the compact drive.
Japanese Published Patent Application No. 2002-336305 describes a gear motor, which does not include a frequency converter, however. Between the gear unit, motor, and brake, as well as between the corresponding housing parts, there are also interfaces that must be precisely manufactured and are therefore complex and expensive.
A frequency converter, which is axially mounted to an electric motor behind its blower and is therefore cooled by its air stream, is described in German Published Patent Application No. 196 22 396. However, this therefore requires a large amount of space and, in addition, a fan that must be able to direct ambient air past.
A piezoelectric brake is described in European Published Patent Application No. 0 694 203.
German Published Patent Application No. 102 07 760 describes an adjusting gear, which, however, requires a large amount of space and an interface to the rotor of the motor.
German Published Patent Application No. 198 48 324 describes a coupling, which, however, requires additional, complicated and expensive machining of the rotationally mounted parts. In particular, not only are the sun and the rotor shaft included, but also a coupling sleeve. A higher number of parts also means higher storage costs.
European Published Patent Application No. 1 081 827 describes an electric tool, in which a gear unit can be driven by an electric motor. However, an interface, which is difficult to manufacture, is provided between the housing parts of the motor and the gear unit.
An axially offset right-angle drive, i.e., a spiroid gear unit, which is connectible to an electric motor and can be driven by it, is described in German Published Patent Application No. 43 09 559.